氫氧化鋁粉對鋁與水化學產氫速率的影響

The influences of Al(OH)3 powder on the hydrogen generation rate from Al/water chemical reaction

溫于傑(Yu-Chieh Wen)

指導教授 ： 王宏文

中原大學/理學院/化學研究所/碩士(2016年)

https://doi.org/10.6840/cycu201600508

摘要

一般常溫常壓下使用鋁粉與水混合的方式來取得氫氣非常困難，由實驗可知加入催化劑氫氧化鋁可以使反應速率加快，並發現莫耳比1:3.5之硝酸鋁與氫氧化鈉混合，在冰浴下合成48 小時的氫氧化鋁擁有不錯的催化效果Al : Al(OH)3 : H2O = 3g : 10g : 30 mL系統中，水溶液pH=12時，90秒內就可以完全產氫完畢並達到100% 理論產氫量。 經由場發射掃描式電子顯微鏡 ( FE-SEM ) 顯示此氫氧化鋁擁有片狀外形、顆粒較細(~100-300nm)，並且在粉末X-Ray繞射儀（Powder X-ray diffraction，XRD）鑒定下為Bayerite晶向結構。
雖然自製條件之氫氧化鋁對於鋁與水產氫有很大的幫助， 卻有著產量太少且製備時間過長等等的缺點， 因此本研究專注於催化劑製備上對於鋁水產氫效果的影響， 為了節省催化劑的用量而嘗試新的快速產氫比例，在更少的 比例下可以得到原先大分量比例一樣的反應效果，並且藉由不同的球磨方式，有效的減少催化劑用量而不影響其產氫效果。 此外本研究發現添加CTAB可以促進β相氫氧化鋁的合成， 將原先所需的時間縮短一半即可以產生未添加時更明顯的六角片狀結構與更好的產氫學果。
良好產氫效果的氫氧化鋁皆為片狀結構之β相， 此晶向比起市售非結晶相、α相、AlOOH等氫氧化鋁催化效果都來的優良，為了可以更快速與大量的得到此晶向， 我們研究如何將市售非β相的氫氧化鋁轉變為具有較多活躍位置(active site)的六角形結構。藉由不同濃度硝酸回溶商用氫氧化鋁粉可以成功將其轉相， 並去探討不同廠牌在不同的清洗條件與鹼性濃度下回溶出的產率與產氫效果， 並以我們自行合成的氫氧化鋁當作最佳標準做比較。

關鍵字

鋁 ； 水 ； 氫氣 ； 生產

並列摘要

It is difficult to generate hydrogen from reaction of aluminum powders and water at room temperature under 1 atm . From previous studies, it’s known that aluminum hydroxide is a good catalyst for hydrogen generation from Al/water system, especially those synthesized from 1:3.5 mole ratio (Al(NO)3:NaOH) ice bathed for 48 h. The reaction Al:Al(OH)3:H2O = 3:10:30 system at pH=12 can complete 100% yield of hydrogen generation in 90 s,Aluminum hydroxide powder was observed by field-emission scanning electron microscope (FE-SEM) and Powder X-ray diffraction (XRD). It shows that Al (OH)3 has a flaky shape , small hexagonal plate particles (~ 100-300 nm ) in a Bayerite crystal structure.
Although, the aluminum hydroxide powders synthesized in our laboratory have excellent effect on the hydrogen generation in Al/water system, it still has drawbacks of low yield and lengthy synthesizing time. Therefore, in this study, I focus on how to cut down the duration of synthesizing time by using alternative synthesizing conditions, where a CTAB was added to promote the formation of bayerite phase . In order to reduce the required amount of catalyst while keep the generation rate, I used the milling process for Al and Al(OH)3.
Layer and hexagonal β-phase Al(OH)3 structure is the important key to get good effect of hydrogen generation, compared with commercial Al(OH)3 which are α-phase. In order to form Bayerite Al(OH)3 more efficiently, we modified the commercial α-phase powder into hexagonal-layer β-phase, by dissolving and re-precipitation process.

並列關鍵字

Aluminum ； water ； hydrogen ； generation

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